Ensure await settled() avoids creating an autorun.

addon-test-support/@ember/test-helpers/-utils.ts

@@ -1,5 +1,43 @@
 /* globals Promise */
-import { Promise as RSVPPromise } from 'rsvp';
+
+import RSVP from 'rsvp';
+import Ember from 'ember';
+import { run } from '@ember/runloop';
+import hasEmberVersion from './has-ember-version';
+
+const backburner = (run as any).backburner;
+
+export class _Promise extends RSVP.Promise<void> {}
+
+RSVP.configure('async', (callback, promise) => {
+  if (promise instanceof _Promise) {
+    if (typeof Promise !== 'undefined') {
+      // use real native promise semantics whenever possible
+      Promise.resolve().then(() => callback(promise));
+    }  else {
+      // fallback to using RSVP's natural `asap` (**not** the fake
+      // one configured by Ember...)
+      RSVP.asap(callback, promise);
+    }
+  } else {
+    // this is the default behaviors from Ember:
+    //   https://github.com/emberjs/ember.js/blob/v3.4.6/packages/ember-testing/lib/ext/rsvp.js
+
+    // if schedule will cause autorun, we need to inform the test adapter
+    if (Ember.testing && !backburner.currentInstance) {
+      let adapter = Ember.Test.adapter as any;
+
+      adapter && adapter.asyncStart();
+
+      backburner.schedule('actions', () => {
+        adapter && adapter.asyncEnd();
+        callback(promise);
+      });
+    } else {
+      backburner.schedule('actions', () => callback(promise));
+    }
+  }
+});
 
 export const nextTick: Function =
   typeof Promise === 'undefined' ? setTimeout : cb => Promise.resolve().then(cb);
@@ -10,9 +48,16 @@ export const futureTick = setTimeout;
  @returns {Promise<void>} Promise which can not be forced to be ran synchronously
 */
 export function nextTickPromise() {
-  return new RSVPPromise(resolve => {
-    nextTick(resolve);
-  });
+  // Ember 3.4 removed the auto-run assertion, in 3.4+ we can (and should) avoid the "psuedo promisey" run loop configuration
+  // for our `nextTickPromise` implementation. This allows us to have real microtask based next tick timing...
+  if (hasEmberVersion(3,4)) {
+    return _Promise.resolve();
+  } else {
+    // on older Ember's fallback to RSVP.Promise + a setTimeout
+    return new RSVP.Promise(resolve => {
+      nextTick(resolve);
+    });
+  }
 }
 
 /**

addon-test-support/@ember/test-helpers/wait-until.ts

@@ -1,5 +1,4 @@
-import { Promise } from 'rsvp';
-import { futureTick } from './-utils';
+import { futureTick, _Promise as Promise } from './-utils';
 
 const TIMEOUTS = [0, 1, 2, 5, 7];
 const MAX_TIMEOUT = 10;